Field
Embodiments disclosed herein generally relate to a magnetic disk device employing a heat assisted magnetic recording (HAMR) head.
Description of the Related Art
In a magnetic disk device that employs a HAMR head, a near-field transducer (NFT) may be utilized to locally heat magnetic media having high coercivity during recording to lower the coercivity of the localized region. Gold is typically used for the NFT material to achieve a high optical efficiency, but the melting point of gold is low and deformation of the NFT is a problem when the NFT is heated for a long term. The NFT temperature is especially high near the point where the optical near-field is generated, and the maximum temperature may reach more than 150 degrees C. over the operational temperature of the magnetic disk device. When the NFT temperature is more than 150 degrees C. over the operational temperature of the magnetic disk device, atomic diffusion of gold atoms via surface, grain boundary, or lattice increases significantly, causing the NFT to deform.
One solution is to use an alloy for the NFT material, which is more stable at elevated temperatures. However, the use of the alloy increases the NFT temperature during operation for two reasons: 1) the imaginary part of the dielectric constant is large, and more light is absorbed by the NFT, and 2) the thermal conductivity of the NFT is lowered due to phonon scattering by dopant atoms, and the heat flow inside the NFT is reduced. If the NFT temperature rise is too high, the benefit of using the alloy may be cancelled out.
Therefore, there is a need in the art for an improved HAMR head.